Morphine hydrochloride trihydrate

Table of contents

• What is morphine hydrochloride trihydrate?
• How does morphine hydrochloride trihydrate work?
• Which conditions is it used or studied for?
• How is morphine hydrochloride trihydrate given?
• What do the clinical trials show?
• What side effects are known?

What is morphine hydrochloride trihydrate?

Morphine hydrochloride trihydrate is a strong pain medicine belonging to the opioid class of drugs. It is a chemically synthesised substance, classified as morphine with the ATC code N02AA01.^[2] In the registry data it appears under the product name Morphine Unimedic 1 mg/ml injektionsvätska, lösning, and it is authorised as a medicine in Sweden.^[1] The substance is the hydrochloride trihydrate salt form of morphine, an opioid that has been used in medicine for many decades. It is listed as a controlled drug in some countries because of its potential for dependence and misuse.^[3]

How does morphine hydrochloride trihydrate work?

Morphine works by attaching to opioid receptors in the brain and spinal cord. These receptors are part of the body's natural pain-control system. When morphine binds to them, it changes the way pain signals are transmitted and perceived, reducing the sensation of pain. The trials listed here use morphine injected directly into the fluid surrounding the spinal cord, a route that places the medicine close to these receptors. The supplementary sources describe morphine sulfate, a related salt form, as an opioid agonist that can cause serious side effects including respiratory depression, meaning slowed or stopped breathing.^[3]

Which conditions is it used or studied for?

• Caesarean section — one Phase 3 trial is studying whether a low dose of spinal morphine controls pain after elective caesarean delivery better than a nerve block.^[2]
• Open colorectal surgery — one Phase 3 trial is studying whether spinal morphine gives recovery quality comparable to epidural pain relief after open bowel surgery.^[1]
• Postoperative pain — both trials focus on pain control in the hours and days after surgery, rather than on treating a long-term disease.

How is morphine hydrochloride trihydrate given?

In the clinical trials listed, morphine hydrochloride trihydrate is given as a solution for injection by the intrathecal route, meaning it is injected into the fluid around the spinal cord.^[2][1] The registry records describe the pharmaceutical form as a solution for injection. The supplementary sources also describe morphine sulfate in oral forms, including extended-release tablets and an oral solution, but these are different salt forms and routes from the intrathecal product used in the trials.^[3][4]

What do the clinical trials show?

Two Phase 3 trials are listed for morphine hydrochloride trihydrate, both authorised and interventional. The first trial, NCT07377630, is a pilot randomised controlled trial in 100 participants having elective caesarean section under spinal anaesthesia. It compares a low dose of intrathecal morphine with a TAP block using ropivacaine and clonidine. The primary endpoint is how many times the somatic pain score at rest reaches 6 or more on a visual analogue scale at several time points up to 24 hours after spinal anaesthesia.^[2]

The second trial, 2024-520262-58-01, involves 124 participants having open colorectal surgery with a midline incision. It compares intrathecal morphine with thoracic epidural analgesia. The primary outcome is the mean Quality of Recovery-15 Swedish version score on postoperative day 2, adjusted for the preoperative score, with a minimally clinically important difference between groups set at 8.^[1]

Both trials measure pain and recovery after surgery. The caesarean section trial focuses on pain scores at rest, while the colorectal surgery trial focuses on patient-reported quality of recovery. The participant populations are adults having planned surgery. The trials are authorised, meaning they have received regulatory approval to proceed. No results are yet reported in the registry data.

What side effects are known?

The supplementary sources describe side effects of morphine sulfate, a closely related salt form of morphine. Common side effects include constipation, nausea, and drowsiness.^[3] Serious side effects include addiction, abuse, and misuse, which can lead to overdose and death. Life-threatening respiratory depression, meaning dangerously slowed or stopped breathing, may occur, especially when starting treatment or increasing the dose.^[3] Neonatal opioid withdrawal syndrome can occur in newborns exposed to morphine during pregnancy.^[3] The sources do not report side effects specific to the intrathecal hydrochloride trihydrate form used in the trials.